Battery pack cooling system

ABSTRACT

A battery pack cooling system includes a plurality of cells disposed in an internal space of a battery pack case so as to form a cooling passage configured to cool the cell modules by cooling air flowing in the cooling passage. The cooling passage includes a cooling air inlet passage, a cooling air exhaust passage, and a plurality of cooling branch passages disposed to connect the cooling air inlet passage and the cooling air exhaust passage in parallel. A minimum temperature sensor is disposed in the upstream position to measure a lowest temperature region in a first cell module. A maximum temperature sensor is disposed in the downstream position which becomes a highest temperature region in the first cell module. Another temperature sensor is disposed in a second cell module to measure the temperature of either the highest temperature or the lowest temperature in the second cell module.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of Ser. No. 14/914,275,filed on Feb. 25, 2016, which is a U.S. National stage application ofInternational Application No. PCT/JP2014/069557, filed Jul. 24, 2014,which claims priority to Japanese Patent Application No. 2013-184608filed in Japan on Sep. 6, 2013, the contents of each of which are hereinincorporated by reference.

BACKGROUND Field of the Invention

The present invention relates to a battery pack cooling system forcooling cell modules by cooling air flowing in a cooling passagedisposed in an internal space of a battery pack case.

Background Information

A conventionally known temperature control device for a battery packcomprises a battery pack for housing a plurality of batteries, ahigh-efficiency heat conducting member disposed between a position inthe battery pack that is the lowest temperature at the time of coolingand a position in the battery pack that is the highest temperature atthe time of cooling, and a temperature measuring means for measuring thetemperature of the high-efficiency heat conducting member. Then, thetemperature inside the battery pack is controlled to within an optimumtemperature range based on the temperature measurement results of thetemperature measuring means (for example, Japanese Laid-Open PatentApplication No. 2013-30375).

SUMMARY

However, in a conventional temperature control device for a batterypack, a thermistor installed in a cooling passage is used as thetemperature measuring device for measuring the temperature of ahigh-efficiency heat conducting member. Consequently, there is theproblem that, while the temperature of the entire battery pack can bemeasured, the temperature distribution of each cooling passage cannot bedetected, and clogging that inhibits the flow of cooling air cannot bedetected. On the other hand, the problem exist that to allow thedetection of clogging and temperature distribution of cooling passages,a plurality of thermistors are required with respect to each coolingpassage, increasing the number of thermistors installed.

In view of the problems described above, an object of the presentinvention is to provide a battery pack cooling system capable ofcontrolling battery temperature, battery input/output control, and cellmodule clogging diagnostics while keeping the number of temperaturesensors installed to a minimum.

In order to achieve the object above, in the present invention, cellmodules formed from a plurality of cells are disposed in an internalspace of a battery pack case, thereby cooling the cell modules bycooling air flowing in a cooling passage that is secured between thecells that are mutually adjacent. In this battery pack cooling system,the cooling passage includes a cooling air inlet passage, a cooling airexhaust passage, and a plurality of cooling branch passages disposed tolink the cooling air inlet passage to the cooling air exhaust passage inparallel. The cell modules are set respectively in the plurality ofcooling branch passages. A minimum temperature sensor is disposed in anupstream position which becomes the lowest temperature, and a maximumtemperature sensor is disposed in a downstream position which becomesthe highest temperature, in one cell module among the plurality of cellmodules. A temperature sensor that measures the temperature of eitherthe highest temperature or the lowest temperature is disposed in one ofthe other cell modules, among the plurality of cell modules. Acontroller that carries out a calculation process based on temperatureinformation from the temperature sensors is provided. The controllercomprises a diagnostic unit that carries out rationality diagnosis ofthe temperature sensors using a difference between temperature changegradients from two minimum temperature sensors in which the minimumtemperatures can be compared, or a difference between temperature changegradients from two maximum temperature sensors in which the maximumtemperatures can be compared.

Thus, a cell module is set to each of the plurality of cooling branchpassages disposed to link the cooling air inlet passage to the coolingair exhaust passage in parallel. Then, a minimum temperature sensor isdisposed in an upstream position which becomes the lowest temperature,and a maximum temperature sensor is installed in a downstream positionwhich becomes the highest temperature, in one cell module among theplurality of cell modules. In addition, a temperature sensor thatmeasures the temperature of either the highest temperature or the lowesttemperature is disposed in one of the other cell modules. That is, theminimum range temperature information can be obtained from a minimumtemperature sensor disposed in an upstream position of a cell modulewhere introduction of cooling air is started, and the maximum rangetemperature information can be obtained from a maximum temperaturesensor disposed in a downstream position of a cell module where thecooling air that has removed heat is discharged. Therefore, batterytemperature control can be carried out using the maximum rangetemperature information, battery input/output control can be carried outusing the minimum range temperature information and the maximum rangetemperature information, and cell module clogging diagnostics can becarried out using the temperature difference information between themaximum range temperature and the minimum range temperature. Inaddition, rationality diagnosis of the temperature sensor (diagnosis onthe presence/absence of rationality) can be carried out using adifference between temperature change gradients from two minimumtemperature sensors in which the minimum temperatures can be compared,or a difference between temperature change gradients from two maximumtemperature sensors in which the maximum temperatures can be compared.As a result, battery temperature control, battery input/output control,and cell module clogging diagnostics can be carried out, while keepingthe number of temperature sensors to three.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the attached drawings which form a part of thisoriginal disclosure.

FIG. 1 is a view illustrating the overall system of a battery packcooling system of the first embodiment applied to a hybrid vehicleequipped with a battery pack.

FIG. 2 is a perspective view illustrating the cell module set in thebattery pack case in the battery pack cooling system of the firstembodiment.

FIG. 3 is a perspective view of a cell can, illustrating therelationship between the temperature and the flow direction of thecooling air in the cell module set in the battery pack case in thebattery pack cooling system of the first embodiment.

FIG. 4 is a flowchart illustrating the flow of fan control steps thatare executed in a hybrid control module (HCM) of the battery packcooling system of the first embodiment.

FIG. 5 is a flowchart illustrating the flow of a battery input/outputcontrol steps that are executed in the hybrid control module (HCM) and alithium ion battery controller (LBC) of the battery pack cooling systemof the first embodiment.

FIG. 6 is an allowable input/output characteristic diagram illustratingthe relationship between the allowable input/output with respect to thecell temperature.

FIG. 7 is a flowchart illustrating the flow of the diagnostic steps thatare executed in the hybrid control module (HCM) of the battery packcooling system of the first embodiment.

FIG. 8 is a view illustrating the overall system of the battery packcooling system, showing another example in which the fan control stepsare directly executed by the lithium ion battery controller (LBC).

DETAILED DESCRIPTION OF THE EMBODIMENTS

Preferred embodiments for realizing the battery pack cooling system ofthe present invention are explained below based on the first embodimentillustrated in the drawings.

First Embodiment

The configuration is described first. The Overall system configuration,Fan control configuration, Battery input/output control configuration,and Diagnostic steps configuration will be separately describedregarding the configuration of the battery pack cooling system of thefirst embodiment.

Overall System Configuration

FIG. 1 illustrates the battery pack cooling system of the firstembodiment applied to a hybrid vehicle equipped with a battery pack;FIG. 2 and FIG. 3 illustrate the configuration of the cell module andtemperature change. The overall system configuration will be describedbelow based on FIG. 1-FIG. 3.

The battery pack cooling system is a system in which cell modules formedfrom a plurality of cells are set in an internal space of a battery packcase so as to have a cooling passage, thereby cooling the cell modulesby cooling air flowing in the cooling passage. The battery pack BPincludes a battery pack case 1, a first partition wall 21, a secondpartition wall 22, a third partition wall 23, a second cell module 31, afirst cell module 32, and a third cell module 33, as illustrated in FIG.1.

The battery pack BP is a secondary battery (lithium ion battery) whichis mounted as a power source for an unillustrated motor/generator 4 fortraveling; the battery pack case 1 is formed from a lower case and anupper case which are joined together, and the internal space of the caseis defined into four chambers by the first partition wall 21, the secondpartition wall 22, and the third partition wall 23.

The second cell module 31, the first cell module 32, and the third cellmodule 33 are disposed, one module each, to three of the four chambersdefined inside the battery pack case 1. A junction box 8 (J/B) whichaggregates a relay circuit for carrying out supply/cutoff/distributionof a heavy current system, and a lithium ion battery controller 9 (LBC)which monitors the battery charge capacity (battery SOC), batterytemperature, and the like, are disposed in the remaining one chamber.

The cooling structure of the cell modules 31, 32, 33 comprises a coolingfan 4, a cooling air inlet duct 5, a cooling branch passage 6, and acooling air exhaust duct 7, as shown in FIG. 1.

The cooling passage includes a cooling air inlet passage 51, a coolingair exhaust passage 71, and three cooling branch passages, a secondcooling branch passage 61, a first cooling branch passage 62, and athird cooling branch passage 63, disposed to link the cooling air inletpassage 51 and the cooling air exhaust passage 71 in parallel.

The cooling fan 4 discharges the cabin interior air (cooling air) takenfrom an intake duct 41, one end of which is opened to the cabininterior, to the cooling air inlet duct 5.

The cooling air inlet duct 5 is formed in a tubular shape by syntheticresin, and is fixed to a long side surface of the battery pack case 1. Acooling air inlet passage 51 is formed by the inner duct space of thiscooling air inlet duct 5, and the cooling air inlet passage 51communicates with each inlet of the cooling branch passages 6 (secondcooling branch passage 61, first cooling branch passage 62, thirdcooling branch passage 63).

The cooling branch passages 6 are formed by three branch passages, thesecond cooling branch passage 61, the first cooling branch passage 62,and the third cooling branch passage 63.

The second cooling branch passage 61 is disposed on the most upstreamside position, of the three branch passages arranged in parallel fromthe upstream side to the downstream side of the flow of the cooling air;the second cell module 31 is set to this second cooling branch passage61.

The first cooling branch passage 62 is disposed in an intermediateposition, of the three branch passages arranged in parallel from theupstream side to the downstream side of the flow of the cooling air; thefirst cell module 32 is set to this first cooling branch passage 62.

The third cooling branch passage 63 is disposed on the most downstreamside position, of the three branch passages arranged in parallel fromthe upstream side to the downstream side of the flow of the cooling air;the third cell module 33 is set to this third cooling branch passage 63.

The cooling air exhaust duct 7 is formed in a tubular shape by syntheticresin, and is fixed to the long side surface of the battery pack case 1that opposes the cooling air inlet duct 5. A cooling air exhaust passage71 is formed by the inner duct space of this cooling air inlet duct 5,and the cooling air exhaust passage 71 communicates with each outlet ofthe cooling branch passages 6 (second cooling branch passage 61, firstcooling branch passage 62, third cooling branch passage 63). The coolingair after cooling taken from this cooling air exhaust duct 7 isdischarged outside of the vehicle.

The cell modules 31, 32, 33 use modules with the same configuration;therefore, as a representative, the configuration of the second cellmodule 31 will be described with reference to FIG. 2. Seven cylindricalshape cell cans 31 a are arranged so that the can axes are parallel toeach other, to configure a first cell can line 31 b and a second cellcan line 31 c. Then, the can axis interval of the second cell can line31 c is shifted by half pitch with respect to the first cell can line 31b and the two layers are superimposed, which are then held by a moduleholder 31 d in a state in which a cold air passage clearance t (forexample, several mm) is secured between mutually adjacent can barrels.At this time, a cold air passage clearance t is also secured between themodule holder 31 d and the cell cans 31 a. Accordingly, cooling air thatis introduced in a direction perpendicular to the can axis of the cellcans 31 a flows drawing a weaving flow line along the surface of the canbarrels of the cell cans 31 a, as illustrated by the arrows in FIG. 2.

The mounting configuration of the thermistors (temperature sensors) tothe cell modules 31, 32, 33 will be described. Four thermistors, a firstthermistor 11 h (first maximum temperature sensor), a second thermistor12L (second minimum temperature sensor), second thermistor 12 h (secondmaximum temperature sensor), and a third thermistor 13L (third minimumtemperature sensor) are provided as thermistors that measure thetemperature utilizing the resistance change with respect to thetemperature change.

The first thermistor 11 h is disposed in a downstream position of thesecond cell module 31, which can become the highest temperature regionin the entire battery pack. This first thermistor 11 h is attached tothe can bottom surface of the cell can that is disposed on the farthestend position on the downstream side of the second cell module 31. Here,the reason why the downstream position of the second cell module 31 canbecome the highest temperature region in the entire battery pack will beexplained. The reason is because, due to the shape of the cooling airinlet duct 5, the cooling air amount to the second cell module 31, whichis on the nearest side from the cooling fan 4, is small; therefore, thecooling effect on the second cell module 31 becomes the lowest among thethree cell modules.

The second thermistor 12L is disposed in an upstream position which canbecome the lowest temperature among the first cell module 32, and thesecond thermistor 12 h is disposed in a downstream position which canbecome the highest temperature among the first cell module 32. Thesesecond thermistors 12L, 12 h are respectively attached to the can bottomsurfaces of cell cans arranged in the two end positions of the firstcell module 32. Here, the reason why the second thermistor 12L and thesecond thermistor 12 h are arranged in the two end positions of thefirst cell module 32 will be explained. When cooling a cell module witha cooling air that flows in one direction, the temperature of the cellcan in an upstream position, which is cooled by a low temperaturecooling air that is discharged from the cooling fan 4, can become thelowest temperature among the first cell module 32, as illustrated inFIG. 3. In contrast, the temperature of the cell can in a downstreamposition, which is cooled by cooling air that becomes a high temperatureby removing heat from the plurality of cell cans through which thecooling air has passed, can become the highest temperature among thefirst cell module 32.

The third thermistor 13L is disposed in an upstream position of thethird cell module 33, which can become the lowest temperature region inthe entire battery pack. This third thermistor 13L is attached to thecan bottom surface of the cell can that is disposed on the farthest endposition on the upstream side of the third cell module 33. Here, thereason why the upstream position of the third cell module 33 can becomethe lowest temperature region in the entire battery pack will beexplained. The reason is because, due to the shape of the cooling airinlet duct 5, the cooling air amount to the third cell module 33, whichis on the farthest side from the cooling fan 4, is large; therefore, thecooling effect on the third cell module 33 becomes the highest among thethree cell modules.

The configuration of the control system using temperature informationfrom the first thermistor 11 h, the second thermistor 12L, the secondthermistor 12 h, and the third thermistor 13L will be described. Thelithium ion battery controller 9 is connected to the hybrid controlmodule 14 (HCM) by a CAN communication line or the like. This hybridcontrol module 14 inputs information from the lithium ion batterycontroller 9, vehicle speed information, engine ON/OFF information, andthe like. Then, the module carries out a fan control (batterytemperature control) by a fan driving instruction to a fan drivingcircuit 15, a battery input/output control by an upper limit torqueinstruction to a motor controller 16 (MC), and diagnostic steps such asclogging diagnostics of the cell module. Detailed contents of the fancontrol, the battery input/output control, and the diagnostic steps willbe described below.

Fan Control Configuration

FIG. 4 illustrates the flow of fan control steps that are executed bythe hybrid control module 14 (HCM). Each of the steps that represent theconfiguration of a fan control unit that controls the battery coolingair amount will be described below, with reference to FIG. 4.

Whether or not the ignition switch is ON is determined in Step S1. Inthe case of YES (IGN ON), the steps proceeds to Step S2 and Step S5, andin the case of NO (IGN OFF), the determination of Step S1 is repeated.

In Step S2, following an IGN ON determination in Step S1 or Step S12,thermistor temperatures Th1, TL2, Th2, TL3 are read from the firstthermistor 11 h, the second thermistor 12L, the second thermistor 12 h,and the third thermistor 13L, and the steps proceeds to Step S3.

In Step S3, following the reading of the thermistor temperatures Th1,TL2, Th2, TL3 in Step S2, a battery FAN speed map that represents therelationship between the thermistor temperature and the FAN speed isread, and the steps proceeds to Step S4. Here, the battery FAN speed mapis set to select a FAN speed that secures the battery performance, fromstepped FAN speeds from FAN speed=0 (fan stopped) to FAN speed=6(maximum fan speed). For example, the FAN speed is increased as thethermistor temperature is increased.

In Step S4, following the reading of the battery FAN speed map in StepS3, a battery request FAN speed is calculated using the battery FANspeed map and the thermistor temperature Th1, which is the highest inthe entire battery pack, and the steps proceeds to step S38.

In Step S5, following an IGN ON determination in Step S1 or Step S12,the vehicle speed and the ENG ON/OFF are read, and the steps proceeds toStep S6.

In Step S6, following the reading of the vehicle speed and the ENGON/OFF in Step S5, a sound vibration FAN speed map, which represents therelationship between the FAN speed with respect to the vehicle speed andthe ENG ON/OFF, is read, and the steps proceeds to Step S7. Here, thesound vibration FAN speed map is set to select a FAN speed that securesthe sound vibration performance, from stepped FAN speeds from FANspeed=0 (fan stopped) to FAN speed=6 (maximum fan speed). For example, ahigher FAN speed is allowed as the vehicle speed of the vehicle isincreased. In addition, a higher FAN speed is allowed when HEV travelingwith the engine ON, compared to when EV traveling with the engine OFF.

In Step S7, following the reading of the sound vibration FAN speed mapin Step S6, a sound vibration request FAN speed is calculated using thevehicle speed, the ENG ON/OFF, and the sound vibration FAN speed map,and the steps proceeds to Step S8. Steps S5-S7 proceed in parallel withSteps S2-S4.

In Step S8, following the calculation of the battery request FAN speedin Step S4 and the calculation of the sound vibration request FAN speedin Step S7, whether or not the battery request FAN speed is FAN speed=6(emergency) is determined. In the case of YES (battery request FANspeed=6), the steps proceeds to Step S9, and in the case of NO (batteryrequest FAN speed≠6), the steps proceeds to Step S10.

In Step S9, following the determination that the battery request FANspeed=6 in Step S8, a Duty according to FAN speed=6 is instructed to thefan driving circuit 15, and the steps proceeds to Step S11.

In Step S10, following the determination that the battery request FANspeed≠6 in Step S8, a Duty that obtains the smaller FAN speed, fromamong the battery request FAN speed and the sound vibration request FANspeed, is instructed to the fan driving circuit 15, and the stepsproceeds to Step S11.

In Step S11, following the instruction to the fan driving circuit 15 inStep S9 or Step S10, an instruction to suppress a change in the FANrotational frequency is outputted when the FAN speed is changed, and thesteps proceeds to Step S12.

Whether or not the ignition switch is OFF is determined in Step S12. Inthe case of YES (IGN OFF), the steps proceed to END, and in the case ofNO (IGN ON), the steps returns to Step S2 and Step S5.

Battery Input/Output Control Configuration

FIG. 5 illustrates the flow of a battery input/output control steps thatare executed in the hybrid control module 14 (HCM) and the lithium ionbattery controller 9 (LBC); FIG. 6 illustrates the relationship betweenthe allowable input/output and the cell temperature. Each of the stepsthat represent the configuration of the input/output control unit thatcontrols the battery input/output will be described below, withreference to FIG. 5 and FIG. 6.

In Step S21, after the input/output control is started, thermistortemperature TL3 by the cell minimum temperature is measured from thefirst thermistor 11 h, the second thermistor 12L, the second thermistor12 h, and the third thermistor 13L, and the steps proceeds to Step S23.

In Step S22, after the input/output control is started, thermistortemperature Th1 by the cell maximum temperature is measured from thefirst thermistor 11 h, the second thermistor 12L, the second thermistor12 h, and the third thermistor 13L, and the steps proceeds to Step S23.

In Step S23, following the measurement of the thermistor temperature TL3by the cell minimum temperature in Step S21 and the measurement of thethermistor temperature Th1 by the cell maximum temperature in Step S22,an input/output MAP (FIG. 6) showing the relationship between theallowable input/output torque and the battery temperature is read, andthe steps proceeds to Step S24. Here, in the input/output MAP, theallowable input/output torque is maximum when the battery temperature isbetween T1−T2, as illustrated in FIG. 6. However, in a low temperaturerange that it equal to or less than battery temperature T1, theallowable input/output torque is limited more as the battery temperatureis reduced. In addition, in a high temperature range that is equal to orgreater than battery temperature T2, the allowable input/output torqueis limited more as the battery temperature is increased.

In Step S24, following the reading of the input/output MAP in Step S23,the allowable input/output torque is determined by select-low using thethermistor temperature TL3 (MIN) by cell minimum temperature and thethermistor temperature Th1 (MAX) by cell maximum temperature and theinput/output MAP, the allowable input/output torque information istransmitted to the hybrid control module 14 (HCM), and the stepsproceeds to Step S25.

In Step S25, following the transmission of the allowable input/outputtorque information to the HCM in Step S24, an upper limit torqueinstruction is outputted from the hybrid control module 14 to the motorcontroller 16 (MC), and the steps proceeds to END.

Diagnostic Steps Configuration

FIG. 7 illustrates the flow of the diagnostic steps that are executed bythe hybrid control module 14 (HCM). Each of the steps that represent thediagnostic unit, which carries out sensor rationality diagnostics aswell as clogging diagnostics, in which cooling air flow failure occursin the modules 31, 32, 33, will be described below with reference toFIG. 7. This diagnostic steps are executed by driving the cooling fan 4at a predetermined FAN speed after the ignition switch is turned ON, ina situation in which predetermined changes have appeared in thethermistor temperatures Th1, TL2, Th2, TL3 (diagnostic conditionsestablished status), if the temperature sensor is normal when thebattery is being cooled while maintaining the fan drive state.

In Step S31, the diagnostic step is started after the ignition switch isturned ON, thermistor temperatures Th1, TL2, Th2, TL3 from the firstthermistor 11 h, the second thermistor 12L, the second thermistor 12 h,and the third thermistor 13L are read a plurality of times at a constantcycle, and the steps proceeds to Step S32.

In Step S32, following the reading of the thermistor temperatures Th1,TL2, Th2, TL3 in Step S31, whether or not the signal voltages Txvoutputted from the first thermistor 11 h, the second thermistor 12L, thesecond thermistor 12 h, and the third thermistor 13L are outside of thenormal range (constant 1≤Txv≤constant 2) is determined. In the case ofYES (Txv<constant 1 or Txv>constant 2), the steps proceeds to Step S34,and in the case of NO (constant 1≤Txv≤constant 2), the steps proceeds toStep S33.

In Step S33, following the determination that constant 1≤Txv≤constant 2in Step S32, a sensor rationality diagnostics on whether or not it isirrational is carried out, based on the thermistor temperatures Th1,TL2, Th2, TL3 from the first thermistor 11 h, the second thermistor 12L,the second thermistor 12 h, and the third thermistor 13L. In the case ofYES (no rationality), the steps proceeds to Step S34, and in the case ofNO (there is rationality), the steps proceeds to Step S35.

In a sensor rationality diagnostics, it is diagnosed as no rationalitywhen a value obtained by subtracting a decreasing gradient ΔTL3 of thethermistor temperature TL3 on the low temperature side from a decreasegradient ΔTL2 of the thermistor temperature TL2 on the low temperatureside becomes less than a constant (ΔTL2−ΔTL3<constant). This isprimarily due to ΔTL2 (cooling air amount small) becoming >ΔTL3 (coolingair amount large). Additionally, it is diagnosed as no rationality whena value obtained by subtracting a decreasing gradient ΔTh2 of thethermistor temperature Th2 on the high temperature side from a decreasegradient ΔTh1 of the thermistor temperature Th1 on the high temperatureside becomes less than a constant (ΔTh1−ΔTh2<constant). This isprimarily due to ΔTh1 (cooling air amount small) becoming >ΔTh2 (coolingair amount large).

In Step S34, following a YES determination in Step S32 or a YESdetermination in Step S33, a diagnosis result is issued that the firstthermistor 11 h, the second thermistor 12L, the second thermistor 12 h,and the third thermistor 13L are sensor abnormal.

In Step S35, following the determination that there is rationality inStep S33, a comparison value α between the thermistor temperatures Th1,Th2 from the two high temperature side thermistors, first thermistor 11h and second thermistor 12 h, is calculated, and the steps proceeds toStep S36. Here, the comparison value α is calculated from the absolutevalue of the difference between the thermistor temperature Th1 and thethermistor temperature Th2 (α=ABS (Th1−Th2)).

In Step S36, following the comparison of the high temperature sidethermistors in Step S35, a comparison value β between thermistortemperatures Th2, TL2 from the low and high temperature side thermistorssecond thermistor 12 h and second thermistor 12L, which are attached toone first cell module 32, is calculated, and the steps proceeds to StepS37. Here, the comparison value β is calculated from the differencebetween the thermistor temperature Th2 and the thermistor temperatureTL2 (β=Th2−TL2).

In Step S37, following the comparison of the low and high temperatureside thermistors in Step S36, a comparison value γ between thermistortemperatures TL2, TL3 from the two low temperature side thermistors,second thermistor 12L and third thermistor 13L, is calculated, and thesteps proceeds to Step S38. Here, the comparison value γ is calculatedfrom the absolute value of the difference between the thermistortemperature TL2 and the thermistor temperature TL3 (γ=ABS (TL2−TL3)).

In Step S38, following the comparison of the low temperature sidethermistors in Step S37, whether or not the second cell module 31 isclogged is diagnosed, using the comparison value α and the comparisonvalue β. In the case of YES (MD1 clogging present), the steps proceedsto Step S39. In the case of NO (MD1 clogging absent), the steps proceedsto Step S40. Clogging of the second cell module 31 is diagnosed when theconditions of β<threshold value and α>threshold value are established.This is because, if clogging occurs due to an intrusive substance intothe second cooling branch passage 61, the flow of cooling air in thesecond cooling branch passage 61 is stagnated, and the flow of coolingair in the first cooling branch passage 62 and the third cooling branchpassage 63 is also slowed due to increased resistance. Consequently, thetemperature difference between the downstream side and the upstream sideof the first cell module 32 becomes small (β<threshold value), and thethermistor temperature Th1 becomes high (α>threshold value).

In Step S39, following the diagnosis that clogging is present in MD1 inStep S38, a diagnosis result is issued that the second cell module 31set in the second cooling branch passage 61 is clogged.

In Step S40, following the diagnosis that clogging is absent in MD1 inStep S38, whether or not the first cell module 32 is clogged isdiagnosed, using the comparison value β, the thermistor temperature Th1,and the thermistor temperature Th2. In the case of YES (MD2 cloggingpresent), the steps proceeds to Step S41. In the case of NO (MD2clogging absent), the steps proceeds to Step S42. Clogging of the firstcell module 32 is diagnosed when the conditions of β<threshold value andTh1 & Th2>threshold value (or TL2 & TL3>threshold value) areestablished. This is because, if clogging occurs due to an intrusivesubstance into the first cooling branch passage 62, the flow of coolingair in the first cooling branch passage 62 is stagnated, and the flow ofcooling air in the second cooling branch passage 61 and the thirdcooling branch passage 63 is also slowed due to increased resistance.Consequently, the temperature difference between the downstream side andthe upstream side of the first cell module 32 becomes small (β<thresholdvalue), and the thermistor temperatures Th1, TL2, Th2, TL3 become high(Th1 & Th2>threshold value, TL2 & TL3>threshold value).

In Step S41, following the diagnosis that clogging is present in MD2 inStep S40, a diagnosis result is issued that the first cell module 32 setin the first cooling branch passage 62 is clogged.

In Step S42, following the diagnosis that clogging is absent in MD2 inStep S40, whether or not the third cell module 33 is clogged isdiagnosed, using the comparison value β and the comparison value γ. Inthe case of YES (MD3 clogging present), the steps proceeds to Step S43.In the case of NO (MD3 clogging absent), the steps proceeds to Step S44.Clogging of the third cell module 33 is diagnosed when the conditions ofβ<threshold value and γ>threshold value are established. This isbecause, if clogging occurs due to an intrusive substance into the thirdcooling branch passage 63, the flow of cooling air in the third coolingbranch passage 63 is stagnated, and the flow of cooling air in thesecond cooling branch passage 61 and the first cooling branch passage 62is also slowed due to increased resistance. Consequently, thetemperature difference between the downstream side and the upstream sideof the first cell module 32 becomes small (β<threshold value), and thethermistor temperature TL2 becomes high (γ>threshold value).

In Step S43, following the diagnosis that clogging is present in MD3 inStep S42, a diagnosis result is issued that the third cell module 33 setin the third cooling branch passage 63 is clogged.

In Step S44, following the diagnosis that clogging is absent in MD3 inStep S42, the first thermistor 11 h, the second thermistor 12L, thesecond thermistor 12 h, and the third thermistor 13L, which are thetemperature sensors, are diagnosed to be normal.

Next, the actions are described. Upon describing the thermistorattaching action of the present invention in a battery pack in which acell module is set to each of a plurality of cooling branch passagesdisposed to link a cooling air inlet passage to a cooling air exhaustpassage in parallel, if the thermistor attachment patterns areclassified into three patterns, the three patterns will be as follows.

Thermistor Attachment Pattern 1

A pattern in which a thermistor is installed to each of an upstreamposition and a downstream position of only one cell module, of theplurality of cell modules.

Thermistor Attachment Pattern 2

A pattern in which a thermistor is installed to each of an upstreamposition and a downstream position of one cell module, of the pluralityof cell modules. In addition, a thermistor that measures the temperatureof either the highest temperature or the lowest temperature is installedin one of the other cell modules.

Thermistor Attachment Pattern 3

A pattern in which a thermistor is installed to each of an upstreamposition and a downstream position of one cell module, of the pluralityof cell modules. In addition, a thermistor that measures the highesttemperature is installed in one of the other cell modules and athermistor that measures the lowest temperature is installed in the cellmodule that is different from the above two cell modules (the pattern ofthe first embodiment).

The Action according to thermistor attachment pattern 1, Actionaccording to thermistor attachment pattern 2, and Action according tothermistor attachment pattern 3 will be separately described belowregarding the actions of the battery pack cooling system.

Action According to Thermistor Attachment Pattern 1

The thermistor attachment pattern 1 is a pattern in which, in the firstembodiment, the second thermistor 12L is installed in an upstreamposition of the first cell module 32, and the second thermistor 12 h isinstalled in a downstream position of the first cell module 32. That is,the pattern is one in which the first thermistor 11 h and the thirdthermistor 13L are removed in the first embodiment.

In the case of this thermistor attachment pattern 1, minimum rangetemperature information is obtained from the second thermistor 12L whichis installed in an upstream position of the first cell module 32, whereintroduction of cooling air is started. On the other hand, maximum rangetemperature information is obtained from the second thermistor 12 hwhich is installed in a downstream position of the first cell module 32,where the cooling air that has removed heat is discharged.

Therefore, fan control (battery temperature control) can be carried outusing maximum range temperature information (thermistor temperature Th2)from the second thermistor 12 h. That is, the first embodiment isprovided with a first thermistor 11 h that measures the highesttemperature in the entire battery pack. Accordingly, when measuring thebattery request FAN speed in the fan control illustrated in FIG. 4, thebattery request FAN speed is calculated using a battery FAN speed mapand the thermistor temperature Th1 from the first thermistor 11 h. Onthe other hand, the battery request FAN speed is calculated using thebattery FAN speed map and the thermistor temperature Th2, by changingthe thermistor temperature Th1 to the thermistor temperature Th2.However, since the thermistor temperature Th2 becomes the second highesttemperature after the thermistor temperature Th1, battery request FANspeed can be measured with sufficient accuracy.

In addition, battery input/output control can be carried out usingminimum range temperature information (thermistor temperature TL2) fromthe second thermistor 12L and maximum range temperature information(thermistor temperature Th2) from the second thermistor 12 h. That is,the first embodiment includes a first thermistor 11 h that measures thehighest temperature, and a third thermistor 13L that measures the lowesttemperature, in the entire battery pack. Accordingly, when measuring theallowable input/output torque in the battery input/output controlillustrated in FIG. 5, the allowable input/output torque is calculatedusing the thermistor temperature Th1, the thermistor temperature TL3,and the input/output MAP. On the other hand, the allowable input/outputtorque is calculated using the thermistor temperature Th2, thethermistor temperature TL2, and the input/output MAP, by changing thethermistor temperature Th1 to the thermistor temperature Th2, andchanging the thermistor temperature TL3 to the thermistor temperatureTL2. However, since the thermistor temperature Th2 can become the secondhighest temperature after the thermistor temperature Th1, and thethermistor temperature TL2 becomes the second lowest temperature afterthe thermistor temperature TL3, the allowable input/output torque can becalculated with sufficient accuracy.

Furthermore, it is possible to diagnose that one of the modules 31, 32,33 is clogged, using the temperature difference information (=comparisonvalue β) between the maximum range temperature (thermistor temperatureTh2) and the minimum range temperature (thermistor temperature TL2).That is, the first embodiment includes a first thermistor 11 h thatmeasures the highest temperature, and a third thermistor 13L thatmeasures the lowest temperature, in the entire battery pack.Accordingly, in the diagnostic steps illustrated in FIG. 7, it ispossible to perform clogging diagnostics for specifying in which moduleclogging has occurred, of the modules 31, 32, 33. In this respect, as isclear from each of the diagnosis conditions of Step S38, Step S40, andStep S42 illustrated in FIG. 7, the condition β<threshold value isincluded in all of the diagnosis conditions. Accordingly, as long as thecondition β<threshold value can be diagnosed, even if the module inwhich clogging has occurred cannot be specified, it is possible todiagnose that one of the modules 31, 32, 33 is clogged.

As a result, in the case of the thermistor attachment pattern 1, fancontrol (battery temperature control), battery input/output control, andcell module clogging diagnostics can be carried out, while keeping thenumber of temperature sensors (second thermistor 12L, second thermistor12 h) installed to the minimum number of two.

Action According to Thermistor Attachment Pattern 2

The thermistor attachment pattern 2 is a pattern in which, in the firstembodiment, the second thermistor 12L is installed in an upstreamposition of the first cell module 32, and the second thermistor 12 h isinstalled in a downstream position of the first cell module 32. Inaddition, there is a pattern 2-1 in which the first thermistor 11 h isinstalled in a downstream position of the second cell module 31, and apattern 2-2 in which the third thermistor 13L is installed in anupstream position of the third cell module 33. That is, the pattern isone in which either the first thermistor 11 h or the third thermistor13L is removed in the first embodiment.

In the embodiment of the thermistor attachment pattern 2-1 describedabove, minimum range temperature information is obtained from the secondthermistor 12L, maximum range temperature information is obtained fromthe second thermistor 12 h, and maximum temperature information which isthe highest in the entire battery pack is obtained from the firstthermistor 11 h.

Therefore, fan control (battery temperature control) can be carried outusing maximum range temperature information (thermistor temperature Th1)from the first thermistor 11 h. In other words, when measuring thebattery request FAN speed in the fan control illustrated in FIG. 4, ahighly accurate battery request FAN speed can be calculated using abattery FAN speed map and the thermistor temperature Th1 from the firstthermistor 11 h, in the same way as in the first embodiment.

In addition, battery input/output control can be carried out usingminimum range temperature information (thermistor temperature TL2) fromthe second thermistor 12L and maximum range temperature information(thermistor temperature Th1) from the first thermistor 11 h. Therefore,when measuring the allowable input/output torque in the batteryinput/output control illustrated in FIG. 5, the allowable input/outputtorque can be calculated more accurately than in the thermistorattachment pattern 1, insomuch as the maximum temperature informationcan be obtained, by using the thermistor temperature Th1, the thermistortemperature TL2, and the input/output MAP.

Furthermore, clogging diagnostics of the cell modules and sensorrationality diagnostics can be carried out using the comparison value αof the high temperature side thermistors (=ABS(Th1−Th2)), the comparisonvalue β of the low and high temperature side thermistors (=Th2−TL2), andthe two high temperature side thermistor temperatures Th1, Th2. That is,in the diagnostic steps illustrated in FIG. 7, while the comparisonvalue γ of the low temperature side thermistors (=ABS(TL2−TL3)) cannotbe obtained, it is possible to specify that clogging has occurred ineither the second cell module 31 or the first cell module 32, using thecomparison values α, β, and thermistor temperatures Th1, Th2. Then, ifclogging is diagnosed by other than the above, it can be specified thatclogging has occurred in the third cell module 33.

In the case of the thermistor attachment pattern 2-2 described above,minimum range temperature information is obtained from the secondthermistor 12L, maximum range temperature information is obtained fromthe second thermistor 12 h, and lowest temperature information which isthe lowest in the entire battery pack is obtained from the thirdthermistor 13L.

Therefore, fan control (battery temperature control) can be carried outusing maximum range temperature information (thermistor temperature Th2)from the second thermistor 12 h. In other words, when measuring thebattery request FAN speed in the fan control illustrated in FIG. 4, asufficiently accurate battery request FAN speed can be calculated usinga battery FAN speed map and the thermistor temperature Th2 from thesecond thermistor 12 h, in the same way as in the thermistor attachmentpattern 1.

In addition, battery input/output control can be carried out usingminimum range temperature information (thermistor temperature TL3) fromthe third thermistor 13L and maximum range temperature information(thermistor temperature Th2) from the second thermistor 12 h. Therefore,when measuring the allowable input/output torque in the batteryinput/output control illustrated in FIG. 5, the allowable input/outputtorque can be calculated more accurately than in the thermistorattachment pattern 1, insomuch as the minimum temperature informationcan be obtained, by using the thermistor temperature Th2, the thermistortemperature TL3, and the input/output MAP,

In addition, clogging diagnostics of the cell modules and sensorrationality diagnostics can be carried out using the comparison value βof the low and high temperature side thermistors (=Th2−TL2), thecomparison value γ of the low temperature side thermistors(=ABS(TL2−TL3)), and the two low temperature side thermistortemperatures TL2, TL3. That is, in the diagnostic steps illustrated inFIG. 7, while the comparison value α of the high temperature sidethermistors cannot be obtained, it is possible to specify that clogginghas occurred in either the first cell module 32 or the third cell module33, using the comparison values α, γ, and thermistor temperatures TL2,TL3. Then, if clogging is diagnosed by other than the above, it can bespecified that clogging has occurred in the second cell module 31.

As a result, in the case of the thermistor attachment pattern 2, fancontrol (battery temperature control), battery input/output control,cell module clogging diagnostics, and sensor rationality diagnostics canbe carried out, while suppressing the number of temperature sensorsinstalled to three. Then, in the case of thermistor attachment pattern2-1, the control accuracy of the fan control is improved by adding thefirst thermistor 11 h, which obtains maximum temperature information, tothe thermistor attachment pattern 1.

Action According to Thermistor Attachment Pattern 3

The thermistor attachment pattern 3 is a pattern in which the secondthermistor 12L and the second thermistor 12 h are installed in theupstream position and the downstream position of the first cell module32. In addition, the pattern is one in which, in the first embodiment,the first thermistor 11 h is installed in a downstream position of thesecond cell module 31, and the third thermistor 13L is installed in anupstream position of the third cell module 33.

The thermistor attachment pattern 1 is a pattern in which, the celltemperature distribution of a cell module selected as a representative(first cell module 32) from among the three cell modules 31, 32, 33, canbe grasped. The thermistor attachment pattern 2 is a pattern in whichthe cell temperature distribution of the first cell module 32 can begrasped by enlarging to the high temperature side or enlarging to thelow temperature side. In contrast, the thermistor attachment pattern 3is a pattern in which the cell temperature distribution can be enlargedand grasped from the minimum temperature to the maximum temperature,with the cell temperature distribution of the first cell module 32 setas a reference.

Therefore, fan control (battery temperature control) can be carried outusing maximum range temperature information (thermistor temperature Th1)from the first thermistor 11 h. Accordingly, when measuring the batteryrequest FAN speed in the fan control illustrated in FIG. 4, highlyaccurate battery request FAN speed can be calculated using a battery FANspeed map and the thermistor temperature Th1 from the first thermistor11 h.

In addition, battery input/output control can be carried out usingminimum temperature information (thermistor temperature TL3) from thethird thermistor 13L and maximum temperature information (thermistortemperature Th1) from the first thermistor 11 h. Accordingly, whenmeasuring the allowable input/output torque in the battery input/outputcontrol illustrated in FIG. 5, an accurate allowable input/output torquecan be calculated using the thermistor temperature Th1, the thermistortemperature TL3, and the input/output MAP.

In addition, clogging diagnostics of the cell modules and sensorrationality diagnostics can be carried out using the comparison value αof the high temperature side thermistors, the comparison value β of thelow and high temperature side thermistors, the comparison value γ of thelow temperature side thermistors, the two high temperature sidethermistor temperatures Th1, Th2, and the two low temperature sidethermistor temperatures TL2, TL3. That is, in the diagnostic stepsillustrated in FIG. 7, it is possible to specify in which of the secondcell module 31, the first cell module 32, and the third cell module 33clogging has occurred, using the comparison values α, β, γ, and thethermistor temperatures Th1, TL2, Th2, TL3. In addition, in thediagnostic steps illustrated in FIG. 7, a highly accurate sensorrationality diagnostics can be carried out, using the two hightemperature side thermistor temperatures Th1, Th2, and the two lowtemperature side thermistor temperatures TL2, TL3.

As a result, in the case of the thermistor attachment pattern 3, fancontrol (battery temperature control), battery input/output control,cell module clogging diagnostics, and sensor rationality diagnostics canall be carried out with high accuracy, while suppressing the number oftemperature sensors installed to four.

In addition, for example, compared to a case in which two thermistorsare installed per each of the three cell modules 31, 32, 33 (number ofthermistors is six), the number of thermistors installed (four) and thenumber of related parts can be reduced. Accordingly, weight reductionand cost reduction become possible. Additionally, the probability of amalfunction occurring can be reduced by reducing the number ofthermistors.

Furthermore, sensor diagnostics of four thermistors 11 h, 12L, 12 h, 13Lcan be carried out with high accuracy. Accordingly, by being able todetect battery cooling failure before a battery failure occurs, batteryrepair costs and battery replacement costs can be reduced. Furthermore,the on-board diagnostics function can be improved, such as reducingerroneous diagnosis by accurately diagnosing abnormalities of thethermistors 11 h, 12L, 12 h, 13L.

Next, the effects are described. The effects listed below can beobtained with the battery pack cooling system according to the firstembodiment.

(1) A battery pack cooling system in which cell modules 31, 32, 33configured from a plurality of cells (cell cans 31 a) are set in aninternal space of a battery pack case 1 so as to have a cooling passage,thereby cooling the cell modules 31, 32, 33 by cooling air flowing inthe cooling passage, wherein the cooling passage is configuredcomprising a cooling air inlet passage 51, a cooling air exhaust passage71, and a plurality of cooling branch passages 61, 62, 63 disposed tolink the cooling air inlet passage 51 and the cooling air exhaustpassage 71 in parallel, the cell modules 31, 32, 33 are installedrespectively in the plurality of cooling branch passages 61, 62, 63, andtemperature sensors (second thermistors 12L, 12 h) are respectivelyinstalled in an upstream position and a downstream position of one cellmodule (first cell module 32) of the plurality of cell modules 31, 32,33. Accordingly, battery temperature control (fan control), batteryinput/output control, and cell module clogging diagnostics can becarried out, while keeping the number of temperature sensors (secondthermistors 12L, 12 h) installed to a minimum (two).

(2) A minimum temperature sensor (second thermistor 12L) is installed inan upstream position which becomes the lowest temperature, and a maximumtemperature sensor (second thermistor 12 h) is installed in a downstreamposition which becomes the highest temperature, in one cell module(first cell module 32) among the plurality of cell modules 31, 32, 33,and a temperature sensor (the first thermistor 11 h or the thirdthermistor 13L) that measures the temperature of either the highesttemperature or the lowest temperature is installed in one of the othercell modules (the second cell module 31 or the third cell module 33)(FIG. 1). Accordingly, in addition to the effect of (1), batterytemperature control (fan control), battery input/output control, cellmodule clogging diagnostics, and sensor rationality diagnostics can becarried out, while keeping the number of temperature sensors (secondthermistors 12L, 12 h+the first thermistor 11 h or the third thermistor13L) installed to three.

(3) A minimum temperature sensor (second thermistor 12L) is installed inan upstream position which becomes the lowest temperature, and a maximumtemperature sensor (second thermistor 12 h) is installed in a downstreamposition which becomes the highest temperature, in one cell module(first cell module 32) among the plurality of cell modules 31, 32, 33, amaximum temperature sensor (first thermistor 11 h) that measures themaximum temperature is installed in one of the other cell modules(second cell module 31) of the plurality of cell modules 31, 32, 33, anda minimum temperature sensor (third thermistor 13L) that measures theminimum temperature is installed in a cell module that is different fromthe above two cell modules (third cell module 33) of the plurality ofcell modules 31, 32, 33 (FIG. 1). Accordingly, in addition to the effectof (1), fan control (battery temperature control), battery input/outputcontrol, cell module clogging diagnostics, and sensor rationalitydiagnostics can all be carried out with high accuracy, while suppressingthe number of temperature sensors (thermistors 11 h, 12L, 12 h, 13L)installed to four.

(4) The temperature sensor that measures the highest temperature (thefirst thermistor 11 h) is disposed in a downstream position of the cellmodule (second cell module 31), which becomes the highest temperatureregion in the entire battery pack, and the temperature sensor thatmeasures the lowest temperature (the third thermistor 13L) is disposedin an upstream position of the cell module (third cell module 33), whichbecomes the lowest temperature region in the entire battery pack (FIG.1). Accordingly, in addition to the effect of (3), a further improvementin the accuracy of the fan control (battery temperature control),battery input/output control, cell module clogging diagnostics, andsensor rationality diagnostics can be achieved, while suppressing thenumber of temperature sensors (thermistors 11 h, 12L, 12 h, 13L)installed to four.

(5) A second cell module 31, a first cell module 32, and a third cellmodule 33 are set as cell modules respectively in a second coolingbranch passage 61, a first cooling branch passage 62, and a thirdcooling branch passage 63, which are arranged in parallel from theupstream side to the downstream side of the flow of the cooling air, anda first maximum temperature sensor (first thermistor 11 h) is installedin a downstream position of the second cell module 31, a second minimumtemperature sensor (second thermistor 12L) and a second maximumtemperature sensor (second thermistor 12 h) are respectively installedin an upstream position and a downstream position of the first cellmodule 32, and a third minimum temperature sensor (third thermistor 13L)is installed in an upstream position of the third cell module 33 (FIG.1). Accordingly, in addition to the effects of (1)-(4), highly accuratefan control (battery temperature control), battery input/output control,cell module clogging diagnostics, and sensor rationality diagnostics canbe carried out using four temperature sensors (thermistors 11 h, 12L, 12h, 13L), in a battery pack BP in which cell modules 31, 32, 33 arerespectively set in the three cooling branch passages 61, 62, 63.

(6) The cell module 31 is configured by arranging a plurality ofcylindrical shape cell cans 31 a so that the can axes are parallel toeach other, to configure a first cell can line 31 b and a second cellcan line 31 c, which are superposed as two layers so that the can axisinterval is shifted by half pitch, and held in a state in which a coldair passage clearance t is secured between mutually adjacent can barrels(FIG. 2). Accordingly, in addition to the effects of (1)-(5), passageresistance of the cooling air that passes through the cell module 31from the upstream side to the downstream side can be suppressed low, andthe plurality of cell cans 31 a can be cooled effectively by the coolingair.

(7) The temperature sensors are thermistors 11 h, 12L, 12 h, 13L thatmeasure the temperature by utilizing the resistance change with respectto the temperature change, and the thermistors 11 h, 12L, 12 h, 13L arerespectively attached to the can bottom surfaces of cylindrical shapecell cans arranged in the end positions of the cell modules 31, 32, 33(FIG. 3). Accordingly, in addition to the effect of (6), the maximumcell temperature and the minimum cell temperature of the cell modules31, 32, 33 can be accurately obtained, by a configuration that detects,not the ambient temperature, but the temperature of the cell cansthemselves.

(8) A controller (hybrid control module 14) that carries out acalculation step based on temperature information from the temperaturesensors (thermistors 11 h, 12L, 12 h, 13L) is provided, wherein thecontroller (hybrid control module 14) comprises a diagnostic unit (FIG.7) that diagnoses clogging in which cooling air flow failure occurs inthe modules 31, 32, 33, using a difference value (comparison value β:β=Th2−TL2) between the maximum temperature information (thermistortemperature Th2) and the minimum temperature information (thermistortemperature TL2) from one cell module (first cell module 32).Accordingly, in addition to the effects of (1)-(7), clogging diagnosticscan be carried out by grasping the cell temperature distribution of onecell module (first cell module 32) among the cell modules 31, 32, 33.

(9) The diagnostic unit (FIG. 7) carries out a rationality diagnosis ofthe temperature sensors (thermistors 11 h, 12L, 12 h, 13L) using thedifference (ΔTL2−ΔTL3) between the temperature change gradients from twominimum temperature sensors (thermistors 12L, 13L) in which the minimumtemperatures can be compared, and the difference (ΔTh1−ΔTh2) between thetemperature change gradients from two maximum temperature sensors(thermistors 11 h, 12 h) in which the maximum temperatures can becompared. Accordingly, in addition to the effect of (8), sensorrationality diagnostics can be accurately carried out using thetemperature change gradient from two pieces of low temperature sideinformation and the temperature change gradient from two pieces of hightemperature side information.

(10) Controllers (lithium ion battery controller 9, hybrid controlmodule 14) that carry out a calculation step based on temperatureinformation from the temperature sensors (thermistors 11 h, 12L, 12 h,13L) are provided, wherein the controllers (lithium ion batterycontroller 9, hybrid control module 14) comprise an input/output controlunit (FIGS. 5, 6) that controls the battery input/output, using theminimum temperature information (thermistor temperatures TL2 or TL3) andthe maximum temperature information (thermistor temperatures Th1 orTh2). Accordingly, in addition to the effects of (1)-(9), batteryinput/output control that can accurately obtain the allowableinput/output torque can be carried out, using two pieces of temperatureinformation, the minimum temperature information and the maximumtemperature information, related to the temperature dependency of thebattery.

(11) A controller (hybrid control module 14) that carries out acalculation steps based on temperature information from the temperaturesensors (thermistors 11 h, 12L, 12 h, 13L) is provided, wherein thecontroller (hybrid control module 14) comprises a fan control unit (FIG.4) that controls the battery cooling air amount using the maximumtemperature information (thermistor temperature Th1 or Th2).Accordingly, in addition to the effects of (1)-(10), a fan control inwhich the battery temperature is accurately reduced can be carried outusing the maximum temperature information.

The battery pack cooling system of the present invention was describedabove based on the first embodiment, but specific configurations thereofare not limited to the first embodiment, and various modifications andadditions to the design can be made without departing from the scope ofthe invention according to each claim in the Claims.

In the first embodiment, an example was shown in which the fan controlsteps are executed by a hybrid control module 14 (HCM). However, the fancontrol steps may be directly executed in the lithium ion batterycontroller 9 (LBC), as illustrated in FIG. 8.

In the first embodiment, an example was shown in which the three cellmodules 31, 32, 33 are set in three cooling branch passages 61, 62, 63.However, the cell modules can be those that comprise two cell modules orthose that comprise four or more cell modules, as long as there is aplurality of cell modules.

In the first embodiment, an example was shown in which a firstthermistor 11 h is installed in a downstream position of the second cellmodule 31, a second thermistor 12L and a second thermistor 12 h arerespectively installed in an upstream position and a downstream positionof the first cell module 32, and a third thermistor 13L is installed inan upstream position of the third cell module 33, as a thermistorattachment pattern. However, the thermistor attachment pattern is notlimited to the thermistor attachment pattern 3 of the first embodiment,and may be the thermistor attachment pattern 1 in which a thermistor isinstalled in each of an upstream position and a downstream position ofonly one cell module of the plurality of cell modules. Furthermore, thepattern may be the thermistor attachment pattern 2, in which athermistor is installed to each of an upstream position and a downstreamposition of one cell module of the plurality of cell modules, inaddition to which, a thermistor that measures the temperature of eitherthe highest temperature or the lowest temperature is installed in one ofthe other cell modules.

In the first embodiment, an example was shown in which a plurality ofcylindrical shape cell cans 31 a are used as the cell module 31, asillustrated in FIG. 2. However, the cell module may be one in whichcells with different shapes, such as a plurality of cell boxes, areused, as long as the configuration secures a flow of cooling air.

In the first embodiment, an example was shown in which the battery packcooling system of the present invention is applied to a battery packthat is mounted on an FF hybrid vehicle or an FR hybrid vehicle.However, the battery pack cooling system of the present invention may beapplied to a battery pack that is mounted on a plug-in hybrid vehicle oran electric vehicle as well.

It is noted that labels such as first, second and third are merelyexemplary and are interchangeable as described herein.

What is claimed is:
 1. A battery pack cooling system comprising: abattery pack case; a plurality cell modules disposed in an internalspace of the battery pack case so as to form a cooling passage thatcools the cell modules by cooling air flowing in the cooling passage,the cell modules including a first cell, a second cell module and athird cell module, the cooling passage including a cooling air inletpassage, a cooling air exhaust passage, and a plurality of coolingbranch passages disposed to connect the cooling air inlet passage andthe cooling air exhaust passage in parallel, the first cell module beingdisposed in a first cooling branch passage of the plurality of coolingbranch passages, the second cell module being disposed in a secondcooling branch passage of the plurality of cooling branch passages, andthe third cell module disposed in a third cooling branch passage of theplurality of cooling branch passages, the first cooling branch passage,the second cooling branch passage, and the third cooling branch passagebeing arranged in parallel from an upstream side to a downstream side ofthe flow of the cooling air; a first minimum temperature sensor disposedin an upstream position of the first cell module to measure a lowesttemperature region in the first cell module; a second minimumtemperature sensor disposed in an upstream position in the third cellmodule to measure a lowest temperature region in the third cell module;a first maximum temperature sensor disposed in a downstream position ofthe second cell module to measure a highest temperature region in thesecond cell module; a second maximum temperature sensor disposed in adownstream position of the first cell module to measure a highesttemperature region in the first cell module; a controller comprising adiagnostic unit configured to perform rationality diagnosis based ontemperature information from the first minimum temperature sensor, thesecond minimum temperature sensor, the first maximum temperature sensorand the second maximum temperature sensor using at least one of: adifference between temperature change gradients from the first minimumtemperature sensor and the second minimum temperature sensor in which alowest temperature in the first cell module and a lowest temperature inthe third cell module can be compared, and a difference betweentemperature change gradients from the second maximum temperature sensorand the first maximum temperature sensor in which a highest temperaturein the first cell module and the highest temperature in the second cellmodule can be compared.
 2. The battery pack cooling system according toclaim 1, wherein the first maximum temperature sensor is disposed in adownstream position of the second cell module, which becomes a highesttemperature region in an entirety of the battery pack, and the secondminimum temperature sensor is disposed in an upstream position of thethird cell module, which becomes a lowest temperature region in anentirety of the battery pack.
 3. The battery pack cooling systemaccording to claim 1, wherein the first cell module is formed byarranging a plurality of cylindrical shape cell cans so that can axesare parallel to each other to configure a first cell can line and asecond cell can line, which are superposed as two layers so that a canaxis interval is shifted by half pitch, and held in a state in which acold air passage clearance is secured between mutually adjacent canbarrels.
 4. The battery pack cooling system according to claim 3,wherein the first minimum temperature sensor and the second maximumtemperature sensor are thermistors that are configured to measuretemperature by utilizing resistance change with respect to temperaturechange, and the first minimum temperature sensor and the second maximumtemperature sensor are respectively attached to can bottom surfaces ofthe cell cans that are arranged in end positions of the first cellmodule.
 5. The battery pack cooling system according to claim 1, whereinthe diagnostic unit is configured to diagnose clogging in which coolingair flow failure occurs in the cell modules using a difference valuebetween maximum temperature information and minimum temperatureinformation from the first cell module.
 6. The battery pack coolingsystem according to claim 1, wherein the controller comprises aninput/output control unit configured to control a battery input/outputusing minimum temperature information and maximum temperatureinformation.
 7. The battery pack cooling system according to claim 1,wherein the controller comprises a fan control unit configured tocontrol a battery cooling air amount, using maximum temperatureinformation.